1. Field of the Invention
The present invention is directed to communications between and transfer of signals between integrated circuit chips, interconnections between such chips and methods of connecting integrated circuit chips for high speed communications therebetween.
2. Description of the Related Art
The coupling of signals between integrated circuit chips, either on the same circuit board or between boards, is of critical interest. Metal interconnections (i.e., metal backplanes) appear to have reached their speed limits, which are estimated to be in the 100s of Giga-bits-per second (Gbps), for each backplane. Discrete channel fiber-optical connections are being incorporated on top of the metal interconnections, but they too are limited to approximately 10 Gbps per channel.
The LVDS standard (Low Voltage Differential Signaling) is currently a popular standard and is based on differential data transmission. This popularity is mainly driven by the ability of LVDS to deliver high speed transmission without large power consumption. LVDS is a differential scheme, which uses two signal lines (traces or conductors) to convey information, with increased noise tolerance in the form of common-mode rejection being achieved. Because of the improvement in signal-to-noise rejection, the signal swing could be dropped to only a few hundred millivolts. Specifications for the LVDS standard may be found in ANSI/TIA/EIA-644-1995 Electrical characteristics standard titled: “Electrical Characteristics of Low Voltage Differential Signaling (LVDS) Interface Circuits.”
In addition, LVDS offers other benefits that include low voltage power supply compatibility, low noise generation, high noise rejection, robust transmission signals, and integration. For these reasons, it has been deployed across market segments wherever the need for speed exists. Even with all these benefits, there are some limitations in certain applications, including support of multipoint bus configurations, operation from still lower power rail voltage, and extended receiver common-mode range.
Of particular interest and need is the ability to increase transmission power efficiency in terms of data transmission speed per unit of power.